High idle controllers are conventionally employed to increase the rotational speed at which a vehicle's engine idles and thus increase the energy output of the vehicle's charging system. Such an increase can be useful to maintain battery charge in the face of unusually high current demands. As pointed out in U.S. Pat. No. 6,573,614 to Doll, for example, police vehicles often have numerous specialized electrical and electronic systems that can place a heavy energy demand on the vehicle alternator when the vehicle is parked, as at an accident scene, running at idle speed for a long period of time.
Traditionally, a motor vehicle's engine throttle is controlled via mechanical linkage to an accelerator pedal. Known systems for increasing idle speed in such vehicles include that disclosed in U.S. Pat. No. 4,527,112 to Herman, in which an electrically controllable mechanical device holds an engine throttle control somewhat more open than its normal idle position.
Motor vehicles of more recent manufacture use a “drive-by wire” system in which the accelerator pedal mechanically connects to one or more potentiometers, which provide electrical input to an electronic control module that in turn controls the engine's throttle with some electromechanical structure. The Doll patent discloses an electronic device for controlling the idle speed of such a vehicle's engine to maintain a high output voltage level of the vehicle's engine-driven alternator. The device takes over control of the idle speed of the engine from a conventional electronic control module. Instead of the electronic control module operating an engine idle speed control device such as a valve or other type of throttle, Doll's disclosed electronic device performs that function, responsive to output signals (intended for such operation) from the electronic control module.
Another known approach, employed in the “Throttle Commander” product manufactured by VMAC, is to plug a device directly into the accelerator pedal.